The changes in SF-36, WOMAC, LEAS, and HHS were evaluated with the Wilcoxon signed-rank test. Offset and leg length were evaluated also with the Wilcoxon signed-rank test. All statistical analysis was performed using SPSS® 15.0 for Windows® (SPSS Inc, Chicago, IL).
SF-36 outcome values improved from a preoperative mean of 68 (range, 60-77) to a mean of 82 (range, 68-92) at the latest followup. WOMAC outcome values improved from 19 (range, 16-21) to 8 (range, 4-12). LEAS outcome values improved from 7 (range, 6-14) to 13 (range, 11-17). HHS also improved from 62 (range, 58-69) to 77 (range, 72-84) with 108 patients (111 hips [91%]) achieving hip scores of more than 80 (no use of walking aid and nonpainful hips), although 10 patients (11 hips [9%]) scored less than 80. Mild hip pain was observed in 68 patients (72 hips [59%]).
Femoral component position was achieved in 122 (100%) of the hips with only four (3%) of the stems being in slight varus (< 5° with respect to the neutral axis of the femoral canal). There was no evidence of osteolytic lesions around any stems. Subsidence of the femoral component was less than 5 mm in 122 (98%) hips and averaged 1 mm (range, 0-7 mm) (Fig. 5). One stem (0.8%) showed 5 mm of subsidence, and another stem (0.8%) showed 7 mm of subsidence; both had radiographic evidence of bone ingrowth fixation. As such, the mechanical failure rate of the stem was 0%.
Offset restoration compared with the contralateral side was achieved in 81 (66%) of the hips (Fig. 6). In 19% of the patients, the offset was increased between 3 and 5 mm, and in 16% of the patients, the offset was undercorrected between −3 and −6 mm compared with the contralateral side.
Reoperations of some sort were performed in 10 cases (8%). Dislocation occurred in four (3%) hips at a mean of 11 weeks (range, 6-105 weeks). Two dislocations were treated successfully with temporary bracing; the other two had surgery. Reoperation, with insertion of a constrained acetabular liner, was carried out in two (2%) hips to address recurrent instability as a result of lack of adequate soft tissue tension despite apparent proper component position. No further dislocations occurred in these patients.
Periprosthetic fracture occurred in two (2%) hips. In one case, a greater trochanter avulsion, which occurred 7 months postoperatively, was treated nonoperatively. In the other case, a Vancouver Type B1  periprosthetic fracture, which occurred 6 weeks postoperatively, had open reduction and internal fixation. Other reoperations included hematoma drainage in three (2%) hips and deep infection in two (2%) hips (requiring incision and drainage in two hips); in one of the hips, the infection was controlled, but in the other, resection arthroplasty was required. We identified no component fractures. There were no acetabular failures in this series.
Modular femoral stems are one option for the revision THA surgeon. Modularity allows surgeons to achieve offset restoration, leg length discrepancy correction, and stability independent of distal stem fixation. We evaluated functional outcomes (SF-36, WOMAC, LEAS, and HHS) with the use of a specific revision modular system and determined whether such a system achieved initial distal fixation, femoral offset restoration, leg length equalization, and hip stability. Furthermore, we evaluated any complications related to its use.
We acknowledge limitations of our study. First, we had only one cohort and cannot directly compare these findings with those with other devices. It was, however, a relatively large cohort in which all patients with failed femoral THA were treated with only one revision modular stem system. Second, we had only short- to midterm followup; however, our objectives were met because functional outcome, stem fixation, offset and leg length restoration, and stability are evaluated early. Third, although most of the femoral deformities were classified as Paprosky Types I and II (86%) and a modular stem may not be considered an option by some surgeons, the remainder of patients in our cohort was adequately treated with such a system.
Our observations demonstrate a modular femoral revision stem is useful when dealing with a variety of femoral revision situations. The first priority of the revision operation is to secure adequate initial fixation of the femoral component, which hopefully then translates into secure long-term fixation. Subsidence of the femoral component in this series was minimal with only two stems subsiding greater than 5 mm; however, both stems showed evidence of bone ingrowth fixation at the latest followup, and the subsidence degree in these stems did not result in hip instability (Fig. 5). The mechanical failure rate in this series was 0%. Although extensively coated nonmodular femoral stems are known to have a definite role in reconstruction of deficient femurs during revision THA , one series reporting the minimum 11-year followup of 170 such stems found aseptic loosening of the stem necessitating reoperation in six cases with an additional 4% of the stems being unstable . Other modular stems [15, 19] have also demonstrated mechanical failure rates in the 4% range. The low mechanical failure rate experienced with the modular stem in this report most likely is a result of the ability of the surgeon to separate fixation from all other aspects of the revision procedure such as stability, offset, leg length, and ROM.
Offset and leg length restoration are important goals of the revision procedure and likely play a large role in the functional outcome of the procedure . Very little information is available in the published literature regarding these two issues in the modular revision situation. Our bias is that the use of a modular stem where fixation is achieved independently of all other parameters allows the surgeon more flexibility in properly establishing the mechanical restoration of the hip mechanics. Both leg length and offset correction are critical parameters that need to be addressed. In this study, leg lengths were restored within 5 mm in 77% of patients and offset was restored within 2 mm in 65% of patients. There are no comparisons available within the recent published literature at this time.
Our data suggest a low dislocation rate (3%) compared with other studies with modular stems such as Park et al.  with a 5% dislocation rate, Ovesen et al.  with 6%, and Rodriguez et al.  with 10%. Dislocation can be minimized with modular stems. The offset changes with the size of the cone body for one thing. However, you can change offset by modifying cone body height in combination with neck length. You can maintain a specific leg length but have two different offsets by modulating cone body height (0, +10, etc) and neck length. The etiology of instability in this group of patients is multifactorial. Probably most importantly, these patients often have undergone multiple previous reconstructive procedures that have led to a compromised soft tissue envelope around the hip preventing optimal soft tissue tensioning. Some additional techniques may need to be implemented to further reduce the incidence of instability, including large femoral heads, selective use of constrained cups, and augmentation of the abductor mechanism repair whenever appropriate.
At a mean followup of 4 years with up to 7 years of followup, there have been no fractures of the modular prosthesis. This is a potential problem related to modularity that has limited the application of modular stems to the revision situation. Two other recent reports on modular revision stems [15, 19] both experienced a 1% stem fracture rate. The authors continue to stress the importance of bony support at the modular junction as a way of minimizing this serious complication.
Comparison of findings in our cohort to other studies in which modular stem systems have been used according to the type of femoral defect present is difficult. For instance, Lakstein et al.  used the classification of Saleh et al. , whereas Ovesen et al.  modified the classification of Saleh et al.  for their study, and Rodriguez et al.  used instead the Mallory  classification. Paprosky et al.  used their own classification, but their method of treatment was with extensively porous-coated nonmodular stems. Although our study appears to have had a higher percentage of patients with less severe defects, the initial fixation in the more severely damaged bone situations were equivalent to those achieved in the other studies.
We believe modular femoral components are an important tool in the surgeons’ armamentarium to address most problems encountered when facing a failed femoral component. Another advantage of modular components is the need for a smaller inventory in the operating room, which also decreases overall operating time. Longer-term followup clearly is needed to fully evaluate the ultimate role of these modular revision femoral stems.
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